Apparatus and method for evaluating a target larger than a measuring aperture of a sensor
AssigneeWaveFront Sciences, Inc.
InventorsDaniel R. Neal, Ron R. Rammage, Darrell J. Armstrong, William T. Turner, Justin D. Mansell
Life of this patent
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Abstract
A Shack-Hartmann wavefront sensor having an aperture which is smaller than the size of an object being measured is used to measure the wavefront for the entire object. The wavefront sensor and the object are translated relative to one another to measure the wavefronts at a plurality of subregions of the object. The measured wavefronts are then stitched together to form a wavefront of the object. The subregions may overlap in at least one dimensions. A reference surface may be provided to calibrate the wavefront sensor.
Claims29
A method for reconstructing a wavefront from a target having a plurality of subregions comprising:
- a) illuminating a subregion;
- b) delivering light from the subregion to a spot generator;
- c) detecting positions of focal spots from the spot generator;
- d) determining a wavefront from the subregion from detected focal spot positions;
- e) repeating steps a)-d) until all subregions have been measured, said repeating including illuminating a subregion such that adjacent subregions have an overlapping region;
- and
- f) stitching together wavefronts determined by step d) including using derivatives of the wavefront in the overlapping regions, thereby reconstructing the wavefront from the target.
A metrology system for analyzing an object larger than an aperture of the system comprising:
- a light source;
- a wavefront sensor;
- an optical system for delivering light from the light source onto a portion of the object being measured and for delivering light from the object to the wavefront sensor;
- a translator for adjusting a relative position of the object and the system, the translator adjusting the relative positions such that adjacent measurements have an overlap region;
- and
- a processor for stitching together wavefronts measured by the wavefront sensor for different portions of the object measured at positions provided by the translator, including using derivatives of wavefronts in overlap regions.
Dependencies are inferred from the claim text.